JP2001205652A - Mold for molding optical element, method for manufacturing optical element using the same, optical head, and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for molding an optical element capable of suppressing the generation of burr at the time of molding, a method for manufac turing the optical element using the same, an optical head, and an optical disk device. SOLUTION: The mold for manufacturing the optical element is equipped with an almost cylindrical body mold 11 and the upper and lower molds 12, 13 respectively fitted and inserted in the body mold 11 from above and below and the body mold 11 has a notch part 11b, which becomes a non-contact state with respect to the upper mold 12 or the lower mold 13, provided in a part of the inner peripherals surface 11a thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical element molding die, an optical element manufacturing method using the same, and an optical head and an optical disk apparatus.

[0002]

2. Description of the Related Art Optical elements are used in optical heads and the like of optical disk devices. Conventional methods of molding an optical element using a plastic material include, for example, an injection molding method in which a pellet is heated, kneaded and melted, and injection-filled into a cavity formed by an insert, or a method in which a substantially final shape is obtained by the injection molding. There is a compression molding method in which a processed plastic material is supplied into a mold maintained at a constant temperature and then pressurized (Japanese Patent Laid-Open No. 5-177725). Hereinafter, conventional molding methods, molding dies, and optical elements will be briefly described with reference to the drawings.

FIG. 6 is a schematic sectional view showing a molding state when a conventional molding die is used. Referring to FIG. 6, a conventional molding die includes a trunk die 1 composed of trunk dies 1a and 1b, and an upper die 2 and a lower die 3 which are inserted from above and below the die 1.

An optical element material (polycarbonate) 4a pre-processed into a substantially final shape by injection molding is arranged inside a cavity formed by a body mold 1, an upper mold 2 and a lower mold 3. The mold is heated in advance to a temperature equal to or higher than the deflection temperature under load and lower than the glass transition point by a press head 5 having a heating and pressing mechanism and a press stage 6 having a heating mechanism. When the temperature of the optical element material 4a substantially coincides with the temperatures of the body mold 1, the upper mold 2 and the lower mold 13, and reaches a constant temperature equal to or higher than the deflection temperature under load and lower than the glass transition point, the press head 5 is lowered, After applying a pressing force of about 980 N / cm ² (about 100 kgf / cm ² ) to the optical element material 4 a and deforming and holding it by the mold 2, the pressing force is released, and the upper mold 2 is cooled to the deflection temperature under load. The optical element 4 is removed and removed. FIG. 7 shows a cross-sectional view of the optical element 4 thus formed.

[0005]

However, in the above-mentioned conventional molding method and molding die, the optical element material 4a flows into the clearance between the upper and lower dies and the body die, and the outside of the molded optical element 4 is removed. There is a problem that burrs indicated by length B occur on the radial surface.

[0006] When an optical head or the like is manufactured using an optical element having burrs, it causes a variation in mounting and mounting to equipment and a variation in performance. When attaching an optical element to a device, at least one of the effective surfaces of the optical element is used as a reference.If the burr generated on that surface is large, it is necessary to remove the burr in the post-molding process. there were.
In addition, in the burr removing step, when the optical element is held, the optical element is damaged, and the yield is reduced. Furthermore, since a part of the burr may remain in the molding die, it is necessary to remove a part of the burr remaining in the molding die before performing the next molding. Due to these problems, there is also a problem that the cost of the optical element increases.

In order to solve the above problems, the present invention provides an optical element molding die capable of suppressing the occurrence of burrs during molding.
It is another object of the present invention to provide an optical element manufacturing method using the same, and an optical head and an optical disk device.

[0008]

In order to achieve the above object, an optical element molding die of the present invention is an optical element molding die for manufacturing an optical element by heating and pressing an optical element material. It is characterized by comprising a substantially cylindrical body mold, an upper mold and a lower mold fitted respectively from above and below the body mold, wherein the body mold is provided with a notch on a part of an inner peripheral surface thereof. According to the above configuration, it is possible to suppress occurrence of burrs during molding of the optical element.

In the above optical element molding die, the distance L between the press surface of the lower die and the notch is preferably 2 mm or less. According to the above configuration, it is possible to particularly suppress generation of burrs during molding of the optical element.

The method of manufacturing an optical element according to the present invention is a method of manufacturing an optical element in which an optical element material is placed inside a mold, and then the optical element material is heated and pressed by the mold. The mold is the optical element molding die of the present invention. According to the optical element manufacturing method, it is possible to suppress the occurrence of burrs during molding of the optical element.

In the above manufacturing method, it is preferable that the temperature of the lower mold is higher than the temperature of the upper mold when the optical element material is heated and pressed. According to the above configuration, it is possible to particularly suppress generation of burrs during molding of the optical element.

In the above manufacturing method, the optical element material is preferably spherical. According to the above configuration, when the optical element material is molded by heating and pressing, the deformation proceeds while maintaining the axial symmetry, so that the performance variation can be reduced.

Further, an optical head according to the present invention is an optical head including a light source and an optical element arranged on the optical axis of the light source, wherein the optical element is manufactured by the above-described optical element manufacturing method of the present invention. It is an optical element.

An optical disk apparatus according to the present invention is an optical disk apparatus for recording or reproducing information on or from an optical disk, comprising: a light source; and an optical element disposed between the light source and the optical disk. Is an optical element manufactured by the optical element manufacturing method of the present invention.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) In Embodiment 1, an example of an optical element molding die of the present invention will be described. FIG. 1A is a cross-sectional view of the optical element molding die 10 according to the first embodiment. Referring to FIG. 1A, an optical element molding die 10 includes a substantially cylindrical trunk die 11, and an upper die 12 and a lower die 13 that are respectively inserted from above and below the trunk die 11. Then, the optical element molding die 10 is provided with the optical element material 14 disposed therein.
Is heated and pressed.

FIG. 1B is a plan view of the body mold 11 as viewed from the lower mold 13 side. The body mold 11 has an inner peripheral surface 11a.
Is provided with a cutout portion 11b that is not in contact with the upper mold 12 or the lower mold 13. In FIG. 1, the notch 1
Although the case where 1b is formed on the lower mold 13 side is shown, the case where the notch 11b is formed on the upper mold 12 side may be adopted.

In the optical element molding die 10, the notch 11b is preferably formed so that the distance L between the press surface 13a of the lower die 13 and the notch 11b is 4 mm or less. Further, it is particularly preferable to form notch 11b such that distance L is 2 mm or less.

According to the optical element molding die of the first embodiment, it is possible to suppress the occurrence of burrs when the optical element is heated and pressed.

Embodiment 2 In Embodiment 2, an optical element manufacturing method of the present invention will be described.

In the optical element manufacturing method according to the second embodiment, the optical element material 14 is disposed inside the optical element molding die 10 described in the first embodiment, and the optical element material 14 is heated and pressed by the optical element molding die 10. By doing so, an optical element is manufactured. At this time, it is preferable to perform the heating and pressing under the condition that the temperature of the upper mold 12 and the temperature of the lower mold 13 are different. Further, it is particularly preferable that the temperature of the lower mold 13 be higher than the temperature of the upper mold 12 when the optical element material 14 is molded by heating and pressing.

The optical element material 14 is preferably spherical. Examples of a method of making the optical element material 14 spherical include a method of making the block-shaped optical element material spherical by cutting and a method of making it spherical by injection molding. According to the injection molding, a spherical optical element material can be formed with good productivity and at low cost.

According to the optical element manufacturing method of the second embodiment, an optical element without burrs can be manufactured. By using the optical element manufactured by this optical element manufacturing method for an optical head or an optical disk device, an optical head or an optical disk device with high reliability can be obtained.

Embodiment 3 In Embodiment 3, an example of the optical head of the present invention will be described.

The configuration of the optical head according to the third embodiment is schematically shown in FIG. 2 (hatching is omitted). Referring to FIG. 2, an optical head 20 includes a light source (laser light source) 21 and
A half mirror 22, a collimating lens 23, an optical element (objective lens) 24, and a light receiving element 25 are provided. The optical element 24 is an optical element manufactured by the optical element manufacturing method according to the second embodiment. The optical element 24 is arranged on the optical axis of the light source 21.

In the optical head 20, the light emitted from the light source 21 is reflected by the half mirror 22, and is made substantially parallel by the collimating lens. Next, the substantially parallel light is condensed on the information medium 26 by the optical element 24 and is reflected. The reflected light from the information medium 26 is transmitted to the optical element 24, the collimator lens 23, and the half mirror 22.
And reaches the light receiving element 25. The light receiving element 25 is
The incident light is converted into an electric signal and output. Thus, the information signal recorded on the information medium 26 is reproduced.

In the optical head of the third embodiment, since the optical element of the present invention is used, an optical head having excellent optical performance can be obtained.

The structure of the optical head shown in FIG. 2 is an example, and if the optical head uses the optical element of the present invention,
Other configurations may be any.

Further, an optical element manufactured by the optical element manufacturing method of the present invention may be used for the collimating lens 23.
Thereby, an optical head having particularly excellent optical performance can be obtained.

An optical disk apparatus according to the present invention is an optical disk apparatus for recording or reproducing information on or from an optical disk, comprising: a light source; and an optical element disposed between the light source and the optical disk. Are optical elements manufactured by the manufacturing method of the second embodiment. That is, the optical disk device of the present invention is an optical disk device including the optical head 20. In the above optical disk device, an optical disk device having excellent optical performance can be obtained.

[0031]

The present invention will be described in more detail with reference to the following examples.

In this embodiment, an example in which an optical element is manufactured using the optical element molding die 10 shown in FIG. 1 will be described. Table 1 shows the dimensions of the body mold used in Example 1.

[0033]

[Table 1]

In Table 1, the length below the neck of the lower die (meaning the distance from the press surface 13a of the lower die 13 to the contact surface between the die 11 and the lower die 13) H, the hollow height (the notch 11b) Height)
h and the cutout width (width of the cutout portion 11b) S are the dimensions indicated by H, h, and S in FIG. 1A, respectively. Here, the distance L between the press surface of the lower die and the notch portion is L = (H−
h).

The optical element mold having the barrel mold shown in Table 1 is transferred by a robot (not shown) to a loading stage 31 of a molding apparatus 30 shown in FIG. 3 (hatching is omitted).
The charging door was opened, and the charging was performed on the preheating stage 30a. The loading door is closed until the next mold is loaded. Thereafter, the optical element mold is transferred to the take-out stage 32 via the forming stage 30b, the first cooling stage 30c, and the second cooling stage 30d, and is disassembled by the robot to take out the optical element. The transfer in the molding apparatus is performed by a transfer arm.

Hereinafter, this embodiment will be described in detail. Optical element materials include polyolefin resins (glass transition point Tg
= 140 ° C., deflection temperature under load Tt = 123 ° C.)
The resin block is cut into a spherical shape (with a radius of about 3m
The pre-processed material used in m) was used. Upper mold 12 and lower mold 1
No. 3 is made of a super hard material and processed into a desired shape. Body type 1
1 is made of stainless steel. Optical element 40 to be formed
4A is a plan view, and FIG. 4B is a cross-sectional view.
The schematic shape of the optical element 40 is as follows: radius of curvature R1 = 2 mm, radius of curvature R2 = 7 mm, center thickness t = 1.6 mm, outer diameter =
4.5 mm.

The optical element 40 was molded by the molding apparatus 30 using the optical element molding die and the optical element material. The molding method will be described below.

In each of the stages 30a to 30d, the press stage 33 in contact with the lower mold and the press head 34 for pressurizing the upper mold each have a built-in heater so that the temperature can be freely set. Each stage is heated to a desired temperature in advance, and the system is such that the mold is transported to the next stage after a predetermined time has elapsed. In this embodiment, the molding was performed in 50 seconds. Table 2 shows the set temperature of each stage.

[0039]

[Table 2]

In the molding device 30, after the optical element molding die was conveyed to the preheating stage 30a, the press head 34 was brought into contact with the upper die. In the preheating stage 30a, since the temperature of the optical element material has not reached the deformable temperature, the pressure was set to a small pressure of about 29.4 N (3 kgf) or less. After a lapse of a predetermined time, the optical element molding die was transported by the transport arm to the next molding stage 30b. In the molding stage 30b, the preheating stage 30
As in a, the press head was in contact with the upper die. In the molding stage 30b, after the temperature of the optical element material reached a deformable temperature, molding was performed with a pressure of about 490 N (about 50 kgf). In the molding stage 30b, the temperature of the upper mold and the lower mold rises due to the heat of the heater, and heats the optical element material. At this time, since heat is transmitted to the optical element material from a portion in contact with the upper mold and the lower mold, the temperature of the optical element material rises from both ends.

Next, the optical element molding die was conveyed to the first cooling stage 30c, and the press head 34 was lowered and brought into contact with the upper die as in the case of the preheating stage 30a. The first cooling stage 30c was set to a set temperature at which the molded optical element became equal to or lower than the deflection temperature under load at the end of the tact.

Next, the optical element molding die was conveyed to the second cooling stage 30d, and was cooled by contacting a press head similarly to the first cooling stage 30c. After cooling the optical element to a temperature at which the robot can take out the optical element, the optical element was transferred to the take-out stage 32 outside the molding apparatus. afterwards,
The robot was transferred to a disassembly / assembly stage (not shown) and disassembled, and the optical element was taken out.

FIGS. 5A to 5D are cross-sectional views of the optical element material at the end of molding tact in the preheating stage 30a, the molding stage 30b, the first cooling stage 30c, and the second cooling stage 30d of the molding device 30, respectively. Shown in
As shown in FIG. 5B, the deformation of the optical element material in the molding stage proceeds along the lens transfer surface.
The optical element material reaches the barrel mold. In this state, the optical element material is further pressed and deformed by the pressing force of the press head to transfer the shape of the upper and lower molds. At the end of the tact in the molding stage, the molding of the optical element material ends. During the molding, there is a gap where the optical element material enters in the clearance between the body mold 11 and the upper mold 12, but as shown in Table 2, the temperature of the press head is lower than the temperature of the press stage. The flow of the optical element material into the mold is suppressed, and the optical element material hardly enters the clearance.

On the other hand, there is also a gap for the optical element material to enter into the clearance between the fitting portion between the body mold 11 and the lower mold 13. However, in this embodiment, since the body mold 11 has the cutout portion 11 b, the burr is formed. Can be suppressed. Notch 1
Table 1 shows burrs when the shape of 1b is changed. The burr amount in Table 1 is the length of B in FIG.

When an optical element was molded under the same conditions using a body mold having no notch, the burr amount was 0.1 mm.
Met. On the other hand, in the case where a body having a notch was used, the burr amount was as small as 0.01 mm or less. Also, the distance L between the press surface of the lower die and the notch is set to 4
mm or less, the burr amount is 0.005 mm
It can be: In particular, when the distance L was 2 mm or less as in Samples 4 and 5, burrs did not occur and an optical element having excellent optical performance was obtained. When an optical head and an optical disk device were tested using this optical element, the optical element of this example had a smaller amount of internal strain than the optical element obtained by injection molding.
It was found that the optical head or the optical disk device equipped with the optical element of this example had good initial characteristics.

Further, since the optical element manufactured by the manufacturing method of the present invention has no burrs, particularly when assembling into an optical head, the inclination of the lens effective surface with respect to the optical axis caused by the burrs hardly occurs, and the number of assembly steps is reduced. Can be reduced.

Further, when an optical element manufactured by a conventional manufacturing method is used for an optical head, the bonding layer varies due to the influence of burrs in the step of bonding the bobbin and the optical element when assembling the optical head. However, the optical element of the present invention has solved this problem.

Therefore, an optical disk device equipped with an optical head using the optical element of the present invention has excellent optical performance as compared with the conventional manufacturing method.

Although the embodiments of the present invention have been described with reference to the examples, the present invention is not limited to the above-described embodiments, and can be applied to other embodiments based on the technical idea of the present invention. it can.

For example, in the above-described embodiment, the case where a polyolefin resin is used as an optical element material has been described, but another thermoplastic resin (polycarbonate, acrylic, or the like) may be used. Compared with the conventional case in which the optical element material processed into the substantially final shape is molded, the spherical optical material used in the present embodiment has a longer resin arrival time to the inner diameter surface of the body mold during molding. Therefore, burrs are less likely to occur.

Further, the pressing deformation temperature, the heating time and the holding time, and the cooling time from the pressing deformation temperature to the deflection temperature under load are not limited to those in the above embodiment.

The optical element material may be molded using a molding apparatus that performs preheating, pressure molding and cooling in one stage.

[0053]

As described above, according to the optical element molding die of the present invention, it is possible to suppress occurrence of burrs when molding an optical element material.

Further, according to the optical element manufacturing method of the present invention, it is possible to suppress occurrence of burrs during molding. Therefore, according to the optical element manufacturing method of the present invention, an optical element having high reliability and optical characteristics when incorporated into an optical head or the like can be manufactured. Furthermore, in the optical element manufacturing method of the present invention, it is not necessary to perform a deburring process in a step after molding,
In addition, since there is no flaw or the like generated by the burr removal processing, an optical element can be manufactured with high productivity and high yield.
Therefore, an optical element can be manufactured at low cost. Also,
According to the optical element manufacturing method of the present invention, unlike the conventional manufacturing method, it is possible to suppress the adhesion of the optical element material to the optical element molding die, and thus it is possible to reduce the number of maintenance of the molding die.

Further, in the optical head or optical disk device of the present invention, since the optical element manufactured by the optical element manufacturing method of the present invention is used, an optical head or optical disk device excellent in optical performance can be obtained.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view and FIG. 1B is a plan view of an example of an optical element molding die of the present invention.

FIG. 2 is a schematic view showing an example of the optical head of the present invention.

FIG. 3 is a diagram illustrating an example of a manufacturing apparatus for the optical element manufacturing method of the present invention.

4A is a plan view and FIG. 4B is a cross-sectional view illustrating an example of an optical element manufactured by the optical element manufacturing method of the present invention.

FIG. 5 is a process chart showing a manufacturing process in the optical element manufacturing method of the present invention.

FIG. 6 is a cross-sectional view illustrating an example of a conventional method for manufacturing an optical element.

FIG. 7 is a cross-sectional view illustrating an example of an optical element manufactured by a conventional method for manufacturing an optical element.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 optical element molding die 11 trunk die 11 a inner peripheral surface 11 b cutout portion 12 upper die 13 lower die 13 a press surface 14 optical element material 20 optical head 40 optical element

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shoji Nakamura 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (reference) 4F202 AG19 AH74 AH79 AM03 AM33 AR06 CA09 CB01 CK90 CL02 CN01 5D119 AA38 BA01 JA02 JA43 JA44 NA05

Claims (7)

[Claims] 1. An optical element molding die for manufacturing an optical element by heating and pressing an optical element material, comprising: a substantially cylindrical body mold; and an upper mold respectively fitted from above and below the body mold. And a lower mold, wherein the body mold has a notch on a part of an inner peripheral surface thereof. 2. The optical element molding die according to claim 1, wherein a distance L between the press surface of the lower die and the notch is 2 mm or less. 3. A method for manufacturing an optical element, comprising: placing an optical element material inside a molding die; and heating and pressing the optical element material with the molding die, wherein the molding die is formed. An optical element manufacturing method, characterized in that it is the optical element molding die described in (1). 4. The method of manufacturing an optical element according to claim 3, wherein the temperature of the lower die is higher than the temperature of the upper die when the optical element material is subjected to heat and pressure molding. 5. The optical element material is spherical.
3. The method for producing an optical element according to item 1. 6. An optical head comprising a light source and an optical element arranged on the optical axis of the light source, wherein the optical element is manufactured by the optical element manufacturing method according to claim 3. An optical head, characterized in that the optical element is an optical element. 7. An optical disc device for recording or reproducing information on or from an optical disc, comprising: a light source; and an optical element arranged between the light source and the optical disc, wherein the optical element is An optical disk device, which is an optical element manufactured by the optical element manufacturing method according to any one of items 3 to 5.